This invention relates generally to the field of thermal stabilization of electronic circuits to achieve as constant a performance level as possible despite wide variations of ambient temperature. More particularly, the invention deals with the problem of thermally stabilizing the operating parameters of FET amplifier devices such that widely varying ambient temperatures do not cause appreciable shifts in stage gain, power output, power consumption or other important parameters.
In general, the approaches adopted in the past for dealing with such problems have proceded along two paths: (a) the device or circuit was enclosed within an isothermal envelope such that it no longer encountered varying ambient temperatures, or (b) the inconstant operating parameters were compensated by the inclusion in the circuit of various non-linear elements which had an opposite effect under varying ambient temperatures, and could thus cancel the effect of the shifting operating parameters of the semiconductor devices.
Each of these approaches continues to be used in appropriate circumstances, but each suffers from a number of shortcomings. The maintenance of an isothermal environment around a device or circuit requires extra equipment which is cumbersome, complex and expensive. Moreover, the power consumed by the necessary heating or cooling equipment may represent an intolerable burden in such applications as communications satellites, where available power sources must be strictly conserved.
The use of compensating devices in the concerned circuit is not always an adequate solution to the problem, since the range and characteristics of the available compensating devices may not provide a satisfactory degree of compensation in every instance. Furthermore, the circuit configurations necessary to employ such compensatory devices sometimes entail a limitation on the function of the circuit being compensated.